I recently updated my OS from windows 8 to 8.1. However as soon as i done this all of my Autodesk software stopped working. When starting up the software i received an error message stating "FATAL-ERROR UNHANDLED ACCESS VIOLATION READING 0x0020 ECEPTION AT 4F864c12h". This message occurs when the program is "loading plug-ins acmgd.dll". I have tried uninstalling several times but with no luck. Can anybody help please?   

You did here that there were some reported problems with the 8.1 update didn't you?I would not have uninstalled/reinstalled.First I would have tried finding a Windows Restore point that pre-dated the install of the 8.1 update.If I did not have one then I would have tried a REPAIR of the AutoCAD installation.If that did not work then I would have done a REINSTALL.Finally if that did not work I would have followed AutoDesk's recommended advice for preparing one's system for a clean install which is key to a REINSTALL.Did you at least do the last one?

I did not realize there was an issue with the update until i installed it. I followed the steps on the autodesks website regarding a clean uninstall but the problem still persisted. I have the disks to re install windows 8 but this involves a full system recovery which is last resort.

Did you search for the error message on the AutoDesk website?

yes but with no luck. Through doing some research I have came across a number of people having the same problem with the windows 8.1 update. I have just yet to find any solutions relating to CAD and Revit  

Didn't MS post a new version of the update and didn't they also offer up a fix for systems that were negatively affected by the firtst 8.1 update?

Hello dear, did you find any solution for this problem as I'm facing it myself?